I have identical issue with previous thread, unable to activate notifications from BLE device.
manager.SetNotify succeeds, but DataAvailable event after that is never raised and notifications are not detected. BLE2 Ver.1.36, trying to communicate with BLE Body Thermometer
I have a curious problem using BLE with Android 7 & 8.
Mi app worked for years in versions 6 and lower of Android, and with Bluetooh 3 and BLE. Allways without problems.
I introduced the necessary modifications to run Android 7 and 8.